1. Field of the Invention
The present invention relates to circuit protection devices, and more particularly to devices which during a current overload in the circuit are tripped to remove the load from the line.
2. Description of the Prior Art
In many installations, various loads are sequentially selected to connect to a common power source in order to operate various devices in a particular predetermined sequence. One example of such installation is a remotely controlled irrigation system where a plurality of sequentially selected solenoids control various valves which in turn selectively direct the flow of water to various areas to be irrigated. Where the irrigated area is large, such as a golf course, visual inspection of each valve in conjunction with the status of the controlling selector selecting such valve for operation is difficult. This difficulty in visual diagnosis prevents the isolation of the shorted solenoid. Furthermore, in typical prior art systems of this kind, all solenoids controlling the various valves are typically protected by single fuse or circuit breaker. The disadvantages of the fuse or circuit breaker are that once any of the solenoids has failed the common circuit is opened and all subsequently selected solenoids are therefore connected to an open line. This fusing arrangement renders diagnosis of the system more difficult since only constant monitoring of the circuit breaker or fuse in conjunction with the selector will allow discovery of the faulty load.
Thus, most prior art protection devices do not lend themselves to convenient diagnoses of the failure modes of a large sequential system, nor do the prior art devices provide selective circuit protection which opens the circuit only during the overloaded period.